Problem: Simplify the following expression: $a = \dfrac{-3z + 12}{5z - 1} - \dfrac{2z + 12}{5z - 1}$
Explanation: Since the expressions have the same denominator we simply subtract the numerators: $a = \dfrac{-3z + 12 - (2z + 12)}{5z - 1}$ Distribute the negative sign: $a = \dfrac{-3z + 12 - 2z - 12}{5z - 1}$ Combine like terms: $a = \dfrac{-5z}{5z - 1}$